Abstract
In this study, we present the issues and proposals to use the elastic-plastic response spectrum method for seismic design of piping systems. First, we showed the idea of converting a piping system model with elastic-plastic vibration into a single-degree-of-freedom (SDOF) system model by applying the modal method in the elastic-plastic region. Next, the equivalence of elastic-plastic vibration response between the piping system model and the SDOF system model was examined. In previous studies, the equivalence of the vibration response has not been sufficiently discussed. Hence, the elastic-plastic seismic response analysis was performed using the piping system model and the SDOF system model, and the similarities and differences in the vibration response were investigated. For the piping system model, the basic response characteristics were examined using a straight pipe that does not have the effects of flexibility characteristics and stress indices. It was shown that the maximum responses for both models were almost the same in the small input, but the response of the SDOF system model was further larger than that of the piping system model in the large input with large plasticity. This result suggests that the scope of application should be limited when the elastic-plastic response spectrum method is used for piping systems. In addition, we found that the square root of the sum of squares (SRSS) method popularly used to calculate the maximum response in the response spectrum method is also effective in the elastic-plastic region. Finally, based on the above results, we proposed the modeling and calculation methods when using the elastic-plastic response spectrum method for the piping system.
